A personal portable device such as a cellular phone and a notebook is supplied with power through a chargeable battery. If a voltage of the battery is lowered than a pre-determined level, a user of the personal portable device charges the battery using a charging device and then uses the portable device again.
A battery of a general personal portable device has a contact terminal exposed out so that it may be electrically connected to a charging terminal prepared to a charging device. When charging the battery, the charging terminal of the charging device and the contact terminal of the battery are connected with each other and keep their electrically connected state.
However, since the charging terminal and the contact terminal are exposed out for their connection, they are easily contaminated by impurities and also easily worn away due to frictions between both terminals when the charging terminal and the contact terminal are connected. In addition, the charging terminal and the contact terminal easily corrode due to moisture in the art, so a contact between the charging terminal and the contact terminal becomes inferior. Also, if moisture is penetrated into the battery through a fine gap of the contact terminal while using the battery, the battery may be completely discharged due to a short circuit of its internal circuit, which may cause a fatal problem.
In order to solve these problems, a contact-less charging technique capable of charging a battery of a personal portable device while the battery is coupled with a charger in a wireless method by means of electronic induction phenomenon is recently proposed. The contact-less charging technique is currently widely utilized for daily goods such as electric toothbrushes and electric shavers.
FIG. 1 is a schematic view showing a battery and a charger adopting the conventional contact-less charging method.
Referring to FIG. 1, the charger 10 includes a high frequency power driving means 30 for receiving power from a common AC power source 20 to output a high frequency AC current, and a primary coil 40 supplied with the high frequency AC current from the high frequency power driving means 30 to form a magnetic field M.
In addition, the battery 50 includes a battery cell 60 charged with electric energy, a secondary coil 70 to which a high frequency AC current is induced according to the linkage of the magnetic field M generated in the primary coil 40, a rectifier 80 for converting the high frequency AC current induced in the secondary coil 70 into a DC current, and a constant voltage/constant current supplier 90 for applying the AC current rectified in the rectifier 80 to the battery cell 60.
Here, the constant voltage/constant current supplier 90 is a well-known circuit element widely used in a battery charging device. The constant voltage/constant current supplier 90 plays a role of supplying current to the battery cell 60 constantly at an initial charging stage, and then decreasing supply of current but keeping voltage constantly if a charging voltage of the battery cell 60 slowly increases and then exceeds a certain criterion level.
According to the charger 10 and the battery 50 adopting the contact-less charging method of the prior art, an intensity of the high frequency AC current induced to the secondary coil 70 is proportional to an intensity of the magnetic flux linked to the secondary coil 70. In addition, the intensity of the magnetic flux linked to the secondary coil 70 is changed according to a relative position with the primary coil 40. That is to say, as the secondary coil 70 is positioned closer to the primary coil 40 of the charger 10, an intensity of the magnetic flux linked to the secondary coil 70 is increased, and as a result an intensity of the high frequency AC current induced by the secondary coil 70 is also increased.
Meanwhile, standards of the constant current/constant voltage supplier 90, which is an essential element of a charging circuit module provided to the contact-less chargeable battery 50, are defined according to an intensity of the high frequency AC current induced by the secondary coil 70. However, the intensity of the AC current induced by the secondary coil 70 is changed according to a relative position between the primary coil 40 and the secondary coil 70 as mentioned above.
Thus, if standards of the constant current/constant voltage supplier 90 are defined using a small high frequency AC current, in case the battery 50 is positioned at a position where a large high frequency AC current is induced, overvoltage exceeding the standards may be applied to both ends of the constant current/constant voltage supplier 90 while charging the battery 10, thereby possibly causing a damage on parts.
Considering the above, the charger 10 and the battery 50 adopting the contact-less charging method of the prior art generally employs a structure capable of relatively fixing positions between them at a position where the standards of the constant current/constant voltage supplier 90 are defined.
FIG. 2 is a perspective view showing a coupling state of an electric toothbrush 100 adopting the conventional contact-less charging method.
Referring to FIG. 2, the electric toothbrush 100 includes a toothbrush body 110 having a battery 115 mounted to its lower end, and a charger 120 for charging the battery 115 in a contact-less method. A main groove 130 and an auxiliary groove 140 are prepared at a lower end of the toothbrush body 110, and a main protrusion 150 and an auxiliary protrusion 160 are respectively prepared to an upper portion of the charger 120 with shapes to be matched with the main groove 130 and the auxiliary groove 140.
The toothbrush body 110 and the charger 120 are closely fixed with each other by means of matching of the grooves 130, 140 and the protrusions 150, 160, and as a result relative positions of the charger 120 and the battery 150 provided to the toothbrush body 110 are also closely fixed.
Standards of a constant voltage/constant current supplier 170 provided to the battery 115 are defined with the assumption that the toothbrush body 110 and the charger 120 are closely coupled. Thus, an overvoltage exceeding the standards is not applied to both ends of the constant voltage/constant current supplier 170, and as a result it may be prevented that the constant voltage/constant current supplier 170 is damaged due to an unexpected overvoltage.
However, relative positions of the battery 115 and the charger 120 are strictly restricted as mentioned above, any inconvenience may be caused to a user. That is to say, whenever charging the battery 115 provided to the toothbrush body 110, the user should repeatedly struggle for fixing the toothbrush body 110 at a fixed position based on the charger 120. Thus, in order to maximize the convenience of the user, a new technical alternative capable of overcoming the restriction of relative positions of the battery 115 and the charger 120 is needed.